This invention relates in general to hinges and more particularly to spring hinges.
Whether it be by reason of building code requirements or mere convenience, some architectural doors should close automatically. For example, many building codes require that the doors to individual hotel and motel rooms must close when not otherwise restrained. Also, the doors which lead to fire escapes or service corridors in large buildings should normally be closed and therefore should seek a closed position when released.
Hydraulic door closers will automatically return doors to their closed positions, but these devices are expensive in their own right and are likewise expensive to install. Furthermore, the force exerted by a door closer generally requires reinforcement of the door and likewise the lintel to which the closer is attached.
So-called spring hinges are considerably less expensive than door closers, and provide an acceptable substitute for many doors which should close automatically. The typical spring hinge has relatively large knuckles through which a coil-type torsion spring extends, and this spring is at each of its ends attached to pins. The means for attaching vary. In some, the end of the spring merely winds around the pin and through friction grips the pin. This provides the possibility for slippage, and further requires a relatively large surface area for gripping. Of course, the portion of the spring that grips the pin is rendered ineffective insofar as applying the torque required to close the door on which the hinge is mounted. In others, the endmost convolutions of the spring are directed transversely and are received in slots in the hinge pins. While this arrangement provides a positive connection between the spring and the pins, it sets up high stress concentrations at the endmost convolutions of the spring.
Aside from the problems with the spring attachment, some spring hinges, once they are adjusted, cannot be readjusted to compensate for changes that may occur in the torsional characteristics of the spring. Similarly, certain conditions within a building may vary and require a change in the closing torques exerted by the door hinges. For example, new carpeting or a change in the pressure exerted by the air conditioning system may affect the doors.
Furthermore, all spring hinges of current manufacture are somewhat difficult to adjust and even more difficult to disassemble and likewise reassemble. These problems derive from the fact that the hinge pins are anchored by cross pins, and holes in the hinge pins must be aligned with corresponding holes in the knuckles. Also, the hinges pins, being segmented and detached, cannot be driven from the hinge with a drift as is true of the more traditional solid pin hinges, thus depriving the user of perhaps the most convenient way of removing the door for repairs.